The proposed work continues the originally outlined integrated study of a number of examples of biological motility, emphasizing the various biochemical and phenomenological approaches possible using the slime mold, Physarum polycephalum. Further characterization of plasmodial actin and myosin will focus on a) the apparent meta- stability of the actin, b) the possible absence from this system of tropomyosin- and/or troponin-like modifier proteins, and c) the nature and significance of the polypeptide chain compositional differences between plasmodial and muscle myosins. Emphasis will be placed next on defining the in situ organization of the muscle-like proteins of this primitive motile system: this will involve further studies of the solubility properties of slime mold actomyosin and experiments using heavy-meromyosin decoration to learn whether slime mold "actin" filaments are attached to the cell surface. Attempts will be made to isolate actomyosins from other phases of the slime mold life cycle (microplasmodia, amoeboid gametes) and from other systems (blood platelets, acanthamoebae) known or thought to contain such proteins: the object of such comparative studies is to learn whether the detailed propertis of non-muscle actomyosins can be correlated with such parameters as rate or intensity of motion, potential vs. actual movement, etc. To facilitate evaluation of molecular models of the action of slime mold actomyosin, studies of protoplasmic streaming in living and glycerinated plasmodia will be carried out. Attempts will be made to isolate a Ca ion -pump analogous to the sarcoplasmic reticulum of muscle. Also proposed are experiments on motility-related proteins other than actomyosins. Efforts to isolate microtubule proteins from slime mold plasmodia will continue. Plasmodial nuclei will be isolated and examined, not only for the presence of microtubules, but also for dynein and/or actomyosin. Slime mold amoebae will be cultured and preliminary studies of the amoebo-flagellate transition will be undertaken. Studies of chemotaxis in the plasmodial and/or amoeboid stages of the slime mold life cycle will be initiated.